Corbin JMK-2-H Bullet Jacket Making Kit
The Corbin JMK-2-H Jacket Making Kit, in conjunction with the Corbin Hydro-Press and Corbin CSU-1 Strip Uncoiler, makes a high precision strip jacket drawing system for a fraction of the usual cost for transfer presses and progressive (sequential) dies. Designed to operate in 40 square feet of floor space, the system is also the most compact, affordable, and precise system of drawing bullet jackets in any caliber, from .123 to 1-inch Gatling, including such favorites as the 50 BMG, 308, 243, and 224 calibers in benchrest quality.
Corbin furnishes 50-pound copper coils, typically 1 inch wide by 0.030-thick strip (other sizes and materials available to order). A coil is placed on the three-foot diameter uncoiler spindle, against a steel backing plate. Another plate is placed on the other side to keep the coil secure. The decoiler unit (CSU-1) automatically feeds just enough strip to keep up with the press, sensing the drag on the coil and silently rolling off just enough material to avoid pulling backward on the feed mechanism.
The strip feeds past a sensor standard, with a seven foot spacing between the decoiler unit and the rear of the Hydro-press. The standard press head is removed and the JMK-2 head is installed in its place. The JMK-2 head replaces the entire press head and ram with a sophistocated automatic blanking and cupping mechanism, with a self-contained hitch feed mechanism and lubricator for the strip. Replacement takes about ten minutes.
The strip feeds into the lubricator rollers, which are supplied with oil from a reservoir on top of the device. The heavy clear glass tank lets the operator see the lubricant level at a glance. Felt rollers apply lubricant to both sides of the copper strip as it passes the first stage of the feed device. A hitch feed mechanism then move the strip forward in locked timing with the press head movement, feeding the strip when the die opens. The strip passes into a slot on the die, and a duplex coaxial blanking and cupping die punches a disk and turns it into a thick cup in one stroke.
The cup drops down a chute in the back of the head assembly, where it can be directed into a barrel or other container. The punched strip continues out the front of the press, where it can be fed into a box. The strip will buckle and fold upon itself after a certain amount has been punched and fed into the container. This punched strip is sold for scrap.
A roller cam mechanism on the press head operates the hitch feed. An optional "fail-safe" system can be added to the press head, which detects strip movement and compares it to the press stroke, shutting off the press and feeder if there is a feed failure or if the strip runs out. Otherwise, the operator may simply stay in the room with the press and observe the movement of the punched strip to determine whether the process is operating normally.
The spacing between punched disks can be adjusted electronically by moving the bottom press head movement sensor up or down. This permits adjustment for the minimum amount of scrap or web between disks for any size of disk. Additional sets of dies may be purchased to use with the same strip, assuming the width and thickness is suitable (a wide range of calibers and thicknesses may be drawm from the same strip, but some may require a different width or thickness).
The JMK-2 head and the CSU-1 uncoiler are both rated for a wide range of sizes. The CSU-1 is adjustable for the center ID (or "eye" of the copper coil, and can handle up to 150 pound coils easily. Corbin stocks 50 pound coils because they are easier for a one-man business to handle without additional hoists. The hitch feed mechanism can be adjusted to handle up to 3/4 inch, 1-inch, 1.25-inch, 1.375-inch, 1.50 inch, 1.75 inch, or 2-inch wide strips (or non-standard sizes in between). The heaviest material which feeds well is about 0.075-inches thick, but in most cases all small arms caliber jackets are made from either 1 inch by .030-thick strip, or 1.25 by .050 inch strip.
Jackets of nearly any length can be drawn (most jackets are less than 2 inches long, but the press can draw a 3 inch jacket). The cups that are produced automatically by the first operation are re-drawn from one to four times, making them longer, smaller in diameter, and possibly thinner walled. Wall geometry can be built to order, including multiple tapers, single taper, or constant thickness (a small draft angle is highly desirable for easy removal from the punches, but a nearly straight shank joined to a parallel mouth section is common). The additional drawing dies are used with the standard press head in the CHP-1 Hydro-Press. A second press is useful for higher production, since it elminiates the need to change the press heads in order to finish the jackets. Many calibers may be drawn from one cup, provided that the cup contains sufficient volume of material for the final jacket (obviously a cup optimized for a 3/4-inch long .224 jacket would not have enough metal to form a 1-inch long .458 jacket, but the opposite is possible if somewhat wasteful).
The JMK-2-H Jacket Maker head is normally sold with a CHP-1 Hydro-Press and CSU-1 strip uncoiler, as well as one or more coils of copper strip. The complete system for manufacturing bullet jackets is built to order, for a given jacket. Other jackets that can be made by adding optional redraw and trim dies are discussed during consultation with a client, as well as suggestions for maximizing the efficiency and use of material for a given jacket. Delivery typically takes from 8-10 months, since demand is extremely high, but can be longer depending on the current backlog. Overtime rush jobs can expedite delivery to less than 30 days, by using overtime (weekends, after-hours work that does not slow down any of the regularly scheduled work) at 2 X normal prices for the JMK-2-H. The press and decoiler are available on short notice without overtime work. Only the dies require overtime for faster delivery.